Flue gas generated by the wastewater incineration entrains a large number of ash particles which are composed of alkali substances into the heat recovery steam generator (HRSG). The deposition of particles rich in alkali on the tube surface of heat transfer can reduce the heat transfer efficiency; even cause severe capacity-limiting plugging and unscheduled shutdown. In the present work, a full-scale CFD model based on the Eulerian-Lagrangian scheme is implemented to simulation flue gas turbulent flow and heat transfer as well as the particle transport in the heat recovery boiler. Several User-Defined Functions (UDFs) are developed to predict the particle deposition or rebounding in the thermal boundary layer and detachment of deposited particles from the surface. On a basis of experiments, a new correlation of Young's modulus is proposed to represent particle sticking behavior. The results of numerical simulation which includes deposition rates and deposition distributions with different sizes of particles in the heat recovery boiler show an acceptable agreement with the field measurements.